Car dont sart after sitting all night

TIPPSY

MEMBER

1999 CHEVROLET SUBURBAN

V8

4WD

AUTOMATIC

167,000 MILES

I have a 99 suburban with the 5.7 it runs great all day but if it sits all night it will not start the next morning with out starting add like brake cleaner I have replaced the following egr, map sen, mas sen, idle air crank shaft sen, I also have ckecked fuel press it is 55 lbs I am lost. What to check next

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Wednesday, December 22nd, 2010 AT 12:29 AM

2 Replies

ERNEST CLARK

EXPERT

First of all, test parts before you replace them.

This sounds like your fuel pressure regulator is leaking. When you turn engine off, the FPR is designed to hold pressure at the injectors so fuel is ready to spray at restart. When the FPR goes bad, it'll leak the fuel back to the tank, so the engine has to wait for fuel to reach engine. Some times the leak is fast, sometimes slow.

Hook up pressure gauge and start engine. Then turn it back off. Observe for fifteen minutes. Pressure should stay the same. If it doesn't, restart engine to get pressure back up then shut off and pinch off the fuel supply line. If pressure stops bleeding down, then the fuel check valve in the pump is bad. If it stops bleeding down, it's time to check FPR.

Repeat test, but this time pinch off the fuel return line back to tank. If pressure stops bleeding down, then bad FPR.

Now if pressure doesn't bleed down during any of these test, you can eliminate the Check valve at pump, but not yet the FPR. Remember, it can bleed down very slowly.

So at night when you know you won't be driving anymore. Start engine and make sure PSI reaches normal. Then turn engine off, leaving gauge hooked up. Come back in the morning and check pressure. If it has gone down, bad FPR.